JP2002268401A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing an abnormal image while accomplishing the miniaturization of the device and the reduction of power consumption. SOLUTION: As for a copying machine 1 for transferring a toner image formed on a photoreceptor drum 3 to an intermediate transfer belt 7 in an overlaid state, the machine 1 is provided with a leaf spring 17 for pressing the intermediate transfer belt 7 to the photoreceptor drum 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc. to which an electrophotographic method is applied, and more particularly, to a method in which a toner image formed on an image carrier is superimposed on an intermediate transfer member. The present invention relates to an image forming apparatus for transferring.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus having a belt-shaped intermediate transfer belt using an electrophotographic system, an electrostatic latent image is formed by exposing a photosensitive drum with a laser beam corresponding to image information. After the electrostatic latent image is developed with toner by a developing unit, the toner image is temporarily transferred to an intermediate transfer body, and finally a point image is fixed on a recording paper by a fixing unit to obtain a recorded image.

In this way, a high-quality image is usually obtained in the image forming process. However, when the surface to be scanned of the photosensitive drum is scanned with the light beam, unevenness occurs in the interval between the sub-scanning lines. Sometimes. Causes include rotational speed fluctuation of the motor itself, vibration due to shaft eccentricity, speed fluctuation of the transmission system generated at the meshing portion of the gear, speed fluctuation resulting from natural vibration due to resonance, and the like.

If the rotation speed of the surface to be scanned of the photosensitive drum fluctuates due to such a cause, the writing line interval in the sub-scanning direction becomes inconsistent. Symptoms occur,
The image quality is significantly reduced. This phenomenon becomes more serious as the writing density of an image has recently been increased, or a toner having a small particle diameter of 5.0 to 9.0 μm, which is smaller than the conventional one, has been used and the demand for higher image quality in the market has increased. It is becoming a close-up, and as the reproduction accuracy of development is improved, it becomes a big problem.

It is desired that the speed of the intermediate transfer belt and the photosensitive member does not fluctuate. However, the eccentricity of the center axis of the photosensitive drum or the eccentricity of the shaft holding the intermediate transfer belt causes the intermediate transfer belt and the photosensitive member to move between the intermediate transfer belt and the photosensitive member. When the pressure at the contact portion fluctuates, the load torque of the intermediate transfer belt and the photoconductor drum fluctuates, so that the speed of the intermediate transfer belt and the photoconductor fluctuates.

Therefore, it is important to form an electrostatic latent image by an image writing unit using high-precision optical scanning and a high-precision position control of the surface to be scanned. Conventionally, regarding such position control of the surface to be scanned, a large and heavy flywheel is generally installed on a rotating body such as a photosensitive drum to keep the rotation constant (see, for example, Japanese Patent Application Laid-open No. 4-221974).

[0007]

However, in the technique of increasing the inertia by using a flywheel as described above, it is necessary to use a flywheel having a large weight, which increases the size of the apparatus and the driving required for rotation. There is a problem that the torque increases and the power consumption increases as a result.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of preventing an abnormal image while reducing the size and power consumption.

[0009]

According to a first aspect of the present invention, there is provided an image forming apparatus for transferring a toner image formed on an image bearing member so as to be superimposed on the intermediate transferring member, wherein the intermediate transferring member is transferred to the image bearing member. Characterized in that it comprises a pressing means that presses toward the surface.

According to the first aspect of the present invention, the pressing means presses the intermediate transfer member against the image carrier, so that the pressure at the contact portion between the intermediate transfer member and the image carrier becomes substantially constant. Since the load torque of the transfer body and the image carrier hardly fluctuates, fluctuations in the rotation speed of the image carrier and the intermediate transfer body can be suppressed, and abnormal images such as image pitch unevenness and jitter can be prevented. In particular, even when eccentricity of the rotation axis of the image carrier occurs, the pressure at the contact portion between the image carrier and the intermediate transfer body can be kept constant by the pressing unit pressing the intermediate transfer body against the image carrier. Further, only a pressing means for pressing the intermediate transfer member against the image carrier is provided, and it is not necessary to use a large flywheel as in the related art, so that downsizing and reduction in power consumption can be achieved.

According to a second aspect of the present invention, in the first aspect of the present invention, the pressing means includes a leaf spring.

According to the second aspect of the present invention, the first aspect is provided.
In addition to the effects similar to those of the invention described in (1), only the intermediate transfer member is pressed against the image carrier by the leaf spring, so that the configuration is simple and the cost can be reduced.

According to a third aspect of the present invention, in an image forming apparatus for transferring a toner image formed on an image carrier so as to be superimposed on an intermediate transfer belt, a rotation axis of the image carrier is opposed to the image carrier. Detecting means for detecting the distance between the opposing shaft of the intermediate transfer belt and the driving means for moving the opposing shaft of the intermediate transfer belt, and controlling the distance between the shafts to be constant by a signal from the detecting means. Control means for controlling the driving means.

According to the third aspect of the present invention, the driving means moves the opposing shaft of the intermediate transfer belt under the control of the control means based on the detection signal from the detecting means, so that the inter-axis distance is kept constant. When the pressure at the contact portion between the intermediate transfer member and the image carrier becomes substantially constant, the load torque of the intermediate transfer member and the image carrier becomes less likely to fluctuate. Can be suppressed, and abnormal images such as image pitch unevenness and jitter can be prevented. In addition, the driving unit moves the opposing shaft of the intermediate transfer belt to simply press the intermediate transfer belt against the image carrier, so that it is not necessary to use a large flywheel unlike the related art, so that the size and the consumption are reduced. Power can be reduced.

According to a fourth aspect of the present invention, in the third aspect of the invention, the driving means includes a piezoelectric body.

According to the fourth aspect of the present invention, the third aspect is provided.
Has the same function and effect as the invention described in (1), and simply moves the opposing axis of the intermediate transfer belt by the piezoelectric material which causes physical distortion by applying a voltage, so that the configuration is simple and compact. Can be achieved.

The invention described in claim 5 is the invention according to claim 3 or 4.
In the invention described in (1), the detecting means includes a semiconductor laser.

According to the fifth aspect of the present invention, the third aspect of the present invention is provided.
In addition to the same effects as those of the invention described in the fourth aspect, by detecting the axial distance using a semiconductor laser, the precise axial distance can be measured, so that the detection accuracy by the detecting means is improved.

[0019]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing a copying machine to which the present invention is applied, and FIG.
FIG. 4 is a side view schematically showing a state in which the intermediate transfer belt is pressed against the photosensitive drum 1 by a pressing unit.

As shown in FIG. 1, a copying machine 1 generally includes
A photosensitive drum (image carrier) 3 that is driven to rotate about a rotating shaft 4, a developing device 5 that supplies toner to an electrostatic latent image on the photosensitive drum 3 and develops it as a toner image, And an intermediate transfer belt (intermediate transfer member) 7 on which the toner image is primarily transferred.

The copying machine 1 is configured to feed a transfer paper, a charging device for uniformly charging the photosensitive drum 3, and perform optical writing corresponding to the original image on the charged photosensitive drum 3. An exposure device for forming an electrostatic latent image, a transfer device for secondarily transferring the toner image on the intermediate transfer belt 7 to a transfer sheet fed from a sheet feeding device, a fixing device for fixing the toner image transferred to the transfer sheet, and the like Are arranged, but illustration and description thereof are omitted in the present embodiment.

The developing device 5 includes a yellow developing device 5Y for developing with yellow toner, a magenta developing device 5M for developing with magenta toner, a cyan developing device 5C for developing with cyan toner, and a black toner. And a black developing device 5B that performs development by
The developing devices 5C, 5M, 5C, and 5B are held by the developing device main body. The developing device main body is rotatable, and when the electrostatic latent image formed on the photosensitive drum 1 is developed, the developing device having the toner of the corresponding color is opposed to the photosensitive drum 1 by the rotation. To the position you want.

The intermediate transfer belt 7 is stretched around a drive shaft 9 driven to rotate by a motor (not shown), a driven shaft 11, and an opposing shaft 13 at a position opposing the photosensitive drum 3. The belt surface is moved by the rotational driving of 11 and 13. Intermediate transfer belt 7
Are transferred such that toner images of respective colors formed on the photosensitive drum 1 are superimposed, and the overlapped toner images are collectively transferred to transfer paper by a transfer device.

As shown in FIG. 2, both ends of the opposing shaft 13 of the intermediate transfer belt 7 are provided with holding members 15 having grooves 16 formed therein.
, And the opposing shaft 13 is movable along the groove 16 (see arrow C). A leaf spring (pressing means) 17 is embedded in the groove 16 of the holding member 15. The leaf spring 17 strongly urges the opposing shaft 13 toward the photosensitive drum 3, whereby the intermediate transfer belt 7 is strongly pressed against the photosensitive drum 3.

As described above, the leaf spring 17 presses the intermediate transfer belt 7 against the photosensitive drum 3 so that the rotating shaft 4 of the photosensitive drum 3 and the shafts 9, 11, and 13 of the intermediate transfer belt 7 are provided.
The intermediate transfer belt 7 and the photosensitive drum 3
When the pressure at the contact portion with the roller is substantially constant, the load torque applied to the intermediate transfer belt 7 and the photosensitive drum 3 is less likely to fluctuate. Therefore, fluctuations in the rotation speed of the photosensitive drum 3 and the intermediate transfer belt 7 can be suppressed, and the photosensitive drum 3 and the intermediate transfer belt 7 are driven to rotate at a constant speed. Can be prevented. In addition, this is a simple configuration in which the plate spring 17 for pressing the intermediate transfer belt against the image carrier is provided, so that miniaturization and power consumption can be reduced, and cost can be reduced.

Next, another embodiment will be described. In the description, the same parts as those described above are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 3 is a schematic diagram showing a copying machine according to the second embodiment. In the second embodiment, as shown in FIG. 3, the rotating shaft 4 of the photosensitive drum 3 is provided with a marker 4a for indicating the center position of the rotating shaft. A marker 13a for indicating the center position of the opposing shaft 13 is provided. Also, as shown in FIG.
In the groove 16 of the holding member 15 for holding the voltage, a physical distortion is caused by the voltage application from the negative feedback control unit (control means) 19 which has received the detection signal from the laser-side length detector (detection means) 25. A piezoelectric body (driving means) 21 for moving the opposing shaft 13 of the intermediate transfer belt 7 in the direction of arrow A is provided.

The laser side elongator 25 applies the laser beam to the marker 4 a of the rotating shaft 4 of the photosensitive drum 3 and the intermediate transfer belt 7.
A laser 13 for irradiating the laser beam from the semiconductor laser 27 to the markers 4a and 13a, thereby rotating the photosensitive drum 3 by irradiating the laser beam from the semiconductor laser 27 to the markers 4a and 13a. The center distance X between the center position of the shaft 4 and the center position of the opposing shaft 13 of the intermediate transfer belt 7 is detected.

By using the semiconductor laser 27, the precise distance X between the axes can be detected, so that the detection accuracy of the laser-side length detector 25 is improved. Instead of the markers 4a and 13a, for example, a mirror or the like may be arranged, and the inter-axis distance X may be detected by receiving the laser beam reflected by the mirror.

The negative feedback control section 19 has a predetermined center distance d.
Is provided, and the laser-side elongate device 15 is provided.
Is compared with a predetermined center distance d stored in the memory 23 so that the center distance X detected by the laser-side length detector 15 becomes the predetermined center distance d. A voltage is applied to the piezoelectric body 21.

More specifically, at the contact portion between the photosensitive drum 3 and the intermediate transfer belt 7, the center distance d at which a predetermined pressure is generated is input to the memory 23, and the actual center distance X is determined by the laser side lengthening device 15. Measure with Image formation starts, and the photosensitive drum 3 and the intermediate transfer belt 7 start rotating, and the distance between the rotating shaft 4 of the photosensitive drum 3 and the opposing shaft 13 of the intermediate transfer belt 7 changes due to the influence of eccentricity or the like.

At this time, the changed distance d1 is lengthened by the laser length unit 25, and a voltage is applied to the piezoelectric body 21 by the negative feedback control unit 7 so that the distance becomes constant. The distance X between the rotating shaft 4 of the photosensitive drum 3 and the opposed shaft 13 of the intermediate transfer belt 7 is kept constant by extending or contracting the piezoelectric body 21 by the distance d1 by the applied voltage ( The distance X between the axes is always kept at the set distance d).

As described above, by keeping the center distance X between the photosensitive drum 3 and the intermediate transfer belt 7 constant, the contact portion between the photosensitive drum 3 and the intermediate transfer belt 7 is pressed with a constant pressure. Therefore, rotation fluctuation can be reduced, and occurrence of abnormal images such as image pitch unevenness and jitter due to rotation fluctuation can be prevented.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the first embodiment, the leaf spring 17 is used as the pressing means. However, the present invention is not limited to this. For example, the opposing shaft 13 is pressed or pulled toward the photosensitive drum 3 using a coil spring. Alternatively, the intermediate transfer belt 7 may be pressed against the photosensitive drum 3.

Although the present invention has been applied to the copying machine 1, the present invention is not limited to this.
Similar functions and effects can be obtained by applying the present invention to a facsimile machine or a multifunction peripheral thereof.

[0036]

According to the first aspect of the present invention, the pressing means presses the intermediate transfer member against the image carrier, so that the pressure at the contact portion between the intermediate transfer member and the image carrier becomes substantially constant. Since the load torque of the intermediate transfer member and the image carrier is less likely to fluctuate, fluctuations in the rotation speed of the image carrier and the intermediate transfer member can be suppressed, and abnormal images such as image pitch unevenness and jitter can be prevented. . Further, only a pressing means for pressing the intermediate transfer member against the image carrier is provided, and it is not necessary to use a large flywheel as in the related art, so that downsizing and reduction in power consumption can be achieved.

According to the second aspect of the present invention, the same effects as those of the first aspect of the invention are obtained, and the structure is simple and only the intermediate transfer member is pressed against the image carrier by the leaf spring. Cost can be reduced.

According to the third aspect of the present invention, the distance between the axes is kept constant by the driving means moving the opposing shaft of the intermediate transfer belt under the control of the control means based on the detection signal from the detecting means. Since the pressure at the contact portion between the intermediate transfer body and the image carrier becomes substantially constant, the load torque of the intermediate transfer body and the image carrier becomes difficult to fluctuate. Fluctuations can be suppressed,
An abnormal image such as image pitch unevenness and jitter can be prevented. In addition, the driving unit moves the opposing shaft of the intermediate transfer belt to simply press the intermediate transfer belt against the image carrier, so that it is not necessary to use a large flywheel unlike the related art, so that the size and the consumption are reduced. Power can be reduced.

According to the fourth aspect of the invention, the same effects as those of the third aspect of the invention are obtained, and the opposing shaft of the intermediate transfer belt is moved by the piezoelectric material which causes physical distortion by applying a voltage. Since it is merely moved, the configuration is simple and the size can be reduced.

According to the fifth aspect of the present invention, the same effects as those of the third or fourth aspect of the invention are obtained, and the precise distance between the axes is measured by detecting the distance between the axes using a semiconductor laser. As a result, the detection accuracy of the detection means is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a copying machine to which the present invention is applied.

FIG. 2 shows a photosensitive drum 1 when an intermediate transfer belt is pressed by a pressing unit.
FIG. 4 is a side view schematically showing a state in which the pressing member is pressed.

FIG. 3 is a perspective view schematically showing a copying machine according to a second embodiment.

FIG. 4 is a side view schematically showing a state in which an intermediate transfer belt is pressed against a photosensitive drum by a piezoelectric body.

FIG. 5 is a block diagram for explaining control of a piezoelectric body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier (image forming apparatus) 3 Photoconductor drum (image carrier) 7 Intermediate transfer belt (intermediate transfer body) 17 Leaf spring (pressing means) 19 Negative feedback control part (control means) 21 Piezoelectric body (drive means) 25 Laser side detector (detection means) 27 Semiconductor laser

Claims (5)

[Claims] 1. An image forming apparatus for transferring a toner image formed on an image carrier so as to be superimposed on an intermediate transfer body, comprising: pressing means for pressing the intermediate transfer body toward the image carrier. Image forming device. 2. The image forming apparatus according to claim 1, wherein the pressing unit includes a leaf spring. 3. An image forming apparatus for transferring a toner image formed on an image carrier so as to be superimposed on an intermediate transfer belt, wherein the intermediate transfer belt is located at a position facing the rotation axis of the image carrier and the image carrier. Detecting means for detecting the distance between the axis and the opposite axis, and driving means for moving the opposite axis of the intermediate transfer belt,
An image forming apparatus comprising: a control unit configured to control a driving unit such that an inter-axis distance is constant according to a signal from the detecting unit. 4. The image forming apparatus according to claim 3, wherein the driving unit includes a piezoelectric body. 5. The image forming apparatus according to claim 3, wherein the detecting unit includes a semiconductor laser.